The annual world market for diagnostic equipment based on immunoassays has grown greatly over the past decades. The main reason for the success of immunoassays is that the method is general and easy to adjust to various chemical analytical problems. The use of different types of detection technologies in combination with immunoassays has made it possible to identify and quantify a number of important chemical substances. Depending on the physical measuring principle, different types of detectors are suited for different types of analytical problems. After the introduction of immunoassays, several detectors have been presented and exhibited excellent performance data. One type of detector uses magnetic permeability as a basis for detection. Such a detector, which is described in SE9502902-1 and U.S. Pat. No. 6,110,660, enables quick and easy identification of substances using immunoassay technology. The measurements are performed by samples being placed in a special measuring coil whose inductance is measured and compared with a separate air-filled reference coil. This type of device enables measuring of magnetic permeability in samples, however with the drawback that the temperature-dependent drift limits the susceptibility of the detector. The temperature drift is caused by variations in the temperature of the sample and by the temperature of the measuring and reference coils being differently affected by the actual measuring process.
The present invention solves in a new and effective manner the problem with temperature-dependent drift in measuring magnetic permeability or alternatively relative magnetic permeability. Moreover it is possible to obtain measuring data that are based on average values of several automatic measurements in succession, which increases performance compared to prior art technique.
Other prior art techniques comprise a device based on a sample compartment with an integrated double coil according to SE524168. The device does not, however, comprise an arm by which the sample vessel in an automated manner can be mechanically manipulated for increased performance. In addition, the device is based on the use of two coils whose temperature is changed similarly and whose properties therefore must be matched (harmonised). The present invention is based on a coil whose properties are changed when inserting and removing the sample vessel, the temperature of the coil being kept constant.
Magnetoimmunoassays are based on the principle that a sample vessel, containing one or more magnetic reagents, and a liquid, is supplied with a sample and placed in an instrument for reading the concentration of an analyte. (Kriz et al., Analytical Chemistry 68, p1966 (1996); Kriz et al., Biosensors & Bioelectronics 13, p817 (1998); Larsson K. et al. Analusis 27, p78, 1999).
The above-mentioned documents, SE9502902-1, U.S. Pat. No. 6,110,660, SE524168, and Larsson K. et al. Analusis 27, p78, 1999, describe prior art devices and methods, which use detection of magnetic permeability for quantitative chemical analyses in samples placed in a measuring coil. Said devices and methods do not, however, comprise a movable coil mechanism based on a device for measuring of sample vessels.
Other prior art techniques also comprise a flow detector for liquid chromatography, which is based on measuring of NMR, Nuclear Magnetic Resonance (Spraul M. et al. NMR Biomed 7, 295-303, 1994). This detector does not, however, measure magnetic permeability, which is a macroscopic property with its origin outside the atomic nucleus in a material, contrary to NMR. In addition, this device does not comprise a movable coil mechanism according to the present invention.